Variable pitch propeller



Oct. 25, 1938. w. w. EVERTS VARIABLE PITCH PROPELLER Filed Jan. e, 1938 2 Sheets-Sheet 1 I'VaIier WEI/Gris Oct. 25, 1938. I w; -rs 2,134,661

VARIABLE P I TCH PROPELLER Filed Jan. 6, 1.938 ZSheets-Sheet 2 Walter umvel-ts Patented Oct. 1938 UNITED STATES PATENT OFFICE VARIABLE PITCH PROPELLER Walter W. Everts, Baltimore, Md., assignor to a Everel Propeller Corporation, Baltimore, M6,,

} I a corporation of Maryland A plication January 6, 1938, Serial No. 183,702

4 Claims. (Cl- 170-164) My invention relates to propellers for aircraft, boats, submarines orthe' like.

An important object of the invention is toprovide a propeller'having a blade which is so pivotally mountedthat the pitch of the blade is increased by the action of centrifugal force, which actionis opposed by the action of the fluid medium in which theblade is rotating, whereby the pitch of the blade increases when 10, the pressure of the fluid medium decreases and the speed of rotation of the blade will remain substantially constant.

A further object of the invention is to provide a. fin or blade which isacted upon by'the pressure of the fluidflmedium, caused by the travel of the vehicle, which fin assists the action of centrifugal force inturning the blade for increasing its pitch, during the travel of the vehicle, but will have no such assisting action when the propeller is rotating. while the vehicle is not travelling.

Afurther. object of the invention is to provide a multiple blade propeller, the blades being independently pivotally mounted upon the hub or rotating element, so that their pitches may be varied.

A further object of the invention is to provide a propellerrofftheabovementioned character which is extremelys'imple in constructior-, formed of few partsand-gis reliablein operation.

Other objectsand' advantages of the invention will be apparent during the course of the following description. I

In the accompanying drawings forming a part 5 of this application and in which like numerals are employed to designate like parts throughout the same,

Figure 1 is a front elevationof a propeller embodying my invention, viewed from the front 0 of the aeroplane,

Figure 2 is an edge elevation of the same,

Figure 3 'is an end elevationbf t' e propeller,

Figure 4 is a longitudinal section taken on line 4-4 of Figure 1,

45 Figure 5 is a transverse section taken on line 60 Figure 7 is a similar view showing the blades at the maximum pitch due to the action of-centrifugal force and reduced air pressure,

Figure 8 is a similar view showing the blades movedv beyond the maximum propelling pitch,-

.1: when the thrust of the atmosphere exceeds the l3-|3 of Figure 9, and,

Figure 14 is a transverse section taken on line ll-ll of Figure 9. 15 In the drawings, wherein for the purpose of illustration are shown preferred embodiments of my invention, the numeral l0 designates a rotary driving element, such as the crank'or drive-shaft 'of an internal, combustion engine of an aeroplane. Rigidly mounted upon the shaft I0 is a hub ll, rotating with the drive-shaft. This hub is preferably in the form of a parallelogram,

and is provided upon opposite sides with pairs of knuckles l2 and I3. These knuckles receive 25 diagonally arranged pins or pivot elements It, held therein by any suitable means. The pins l4 are parallel.

The numeral l5 designates blades, formed of any suitable material and twisted to produce the 30 desired pitch. These blades l5 are of the conventional type, having the leading faces l5 convex or cambered. The inner ends or shanks it of these bladesare arranged within sockets l1, including sides l8 and an inner end or base I9.

The shanks it are held within the sockets H by bolts 20 or the like. The inner ends IQ of the sockets are provided with diagonal openings 2!, to pivotally receive the pins Hi. The blades I5 are therefore pivotally mounted upon their hub II to turn upon the pins M. The openings 2i and the pins l4 are all diagonal with respect to the blades. Satisfactory results are obtainable by having these pins and openings disposed at an inclined angle of 30 with respect to the central longitudinal axis 22 of the blades l5. The invention is not restricted to this precise angle arrangement, as the same may be varied, anywhere between 90 and 0 with respect to the longitudinal axis 22. When the number of degrees is reduced, such as below 30, as explained, the changing of the pitch of the blade is increased at a greater rate when the blade is turned upon its diagonal pivot. It is also preferred that the leading and trailingportions 2t and 26 should be unbalanced with the trailing area larger.

An important feature of the invention is the provision of a pressure operated fin or blade 25, which is secured to each blade I5, near the hub II. The fin or blade 25 is Substantially flat on both sides and is not twisted. This fin is sufiiciently stiff to hold its shape against its own weight, but is preferably resilient, and may be formed 'of metal. I have found that it may be formed of spring metal, having a thickness of 52/1000 of an inch. The fin may also be formed much thicker and rigid. This fin 25 has its inher end arranged within a slot or groove 26 cut I E in the shank I6 of the blade I and may be rigidly secured therein by any suitable means as by certain of the bolts 20. If the blade I5 is wooden, the fin 25 may also be formed of wood and glued to the blade iii. If the blade I 5 is metal, the fin 25 could be cast integral with the blade. The fin 25 could also be bolted to one of the sides I8 of the socket H. In any event, the fin or blade 25 is at the trailing edge of the blade I5 near or at the hub or crank shaft. It is preferred that the fin or blade 25 have its longitudinal axis arranged at a right angle to the pin Id, which will enable the fin to have the maximum leverage for utilizing the air pressure in aiding centrifugal force in turning the blade upon the pin it when the aeroplane is travelling.

The inner ends I9 carry stop lugs or extensions 27, arranged within recesses 28, formed in the hub II. These stop lugs limit the swinging movements of the blades on the pins or pivots M, so that the blades cannot fall to inoperative positions, but do not interfere with the normal operation of the blade in varying its pitch.

The operation of the propeller is as follows. When the engine is started, the propeller is turned counter-clockwise, viewed from the front of the aeroplane, which is the practice in the United States.. As soon as the propeller rotates, centrifugal force acting upon each blade I5 tends to move the same to a radial position. This action of centrifugal force is opposed by the air thrust, which tends to swing the blade upon its pivot I4 so that the outer end of the propeller moves forwardly from the radial position. These two opposing forces act against each other and theblade will assume a normal operating position between the extreme forward position and the true radial position. Assuming that the aeroplane is now flying at substantially sea level, the air thrust is at the maximum and the blade has its outer end moved forwardly slightly from the radial position, so that the blade will have the minimum pitch. When the blade is turned upon its diagonal pivot I4 it is also turned upon its longitudinal axis, thereby varying the pitch of the blade. The unbalanced areas 23 and 24 also aid in turning the blade about its longitudinal axis, for when the blade turns upon the diagonal pivot I4 the longitudinal axis of the blade swings about the surface of a cone. The action of centrifugal force tends to move the blade upon its pivot I4 to the true radial position, thereby increasing the pitch of the blade. As the speed of the aeroplane increases, the air pressure acting upon the forward fiat face of the fin 25 tends to turn the blade I5 upon its diagonal pivot I4, thus increasing the pitch of the blade. The fin 25 therefore aids the action of centrifugal force in turning the blade toward the rear or radial position, to increase this pitch. Assuming that the propeller is being driven at 2,000 R. P. M., at sea level, the

areaecr propeller will then have the minimum pitch for this elevation. If the aeroplane now rises to a.

overcome the air thrust upon the propeller blade.

and the propeller blade would be turned upon its diagonal pivot It in a rearward direction, turning the blade about its longitudinal axis for increasing the pitch of the propeller. This increased pitch of the propeller will cause the propeller to drive the aeroplane at an increased speed but the speed of rotation of the propeller will remain constant. The increased speed of the aeroplane will cause the air pressure to act upon the fin or blade 25 which will aid centrifugal force in turning the blade upon its pivot I4 to increase its pitch. By experiments which I have conducted, I have found that by combining the fin or blade 25 with the propeller blade, pivotally mounted as described, that the speed of rotation of the propeller will remain substantially constant, although the pitch of the blade will automatically change, when travelling from one elevation to the other.

Since the fins 25 have their forward and rear faces flat and not cambered, these fins only serve to aid in swinging the blades I5 upon their pivots to increase their pitch, when the aeroplane is travelling, and hence when the propeller is idling with the aeroplane stationary, the fins 25 do not function to vary the pitch of the propeller blades. This is important as it is desired that the blades have the minimum pitch in taking off. The fins 25 will not vary the pitch of the propeller blades when the propeller blades are rotating at any selected speed, provided the aeroplane is held against travelling.

Attention now being called to Figures 9 and 10, the numeral 29 designates a crank shaft or rotary driving element, having a hub 30 rigidly secured thereto. This hub is provided with diametrically oppositely arranged bosses 3|, to which are secured diagonal pivot elements or pins 3|, the inner ends of which may be screwthreaded into the bosses, and held against displacement by any suitable means. The shafts 3| are radial with respect to the crank shaft 29, and the central longitudinal axes of the shafts 3I are arranged to intersect with the central longitudinal axis of the shaft 29. The numeral 32 designates companion oppositely arranged attaching yokes, provided at their ends with collars 33, pivotally mounted upon the shafts 3|, and arranged as shown. These attaching yokes 32 are provided with radially extending sockets 34, preferably formed integral therewith. The sockets 34 receive the shanks 35 of propeller blades 36, which are substantially identical with the propeller blades I5, having the same central longitudinal axis 31, corresponding to the axis 22, and the unbalanced areas, 38 and 39 with the front face of the blade convex or cambered and the rear face substantially fiat, as shown in connection with the first form of propeller. Attention is called to the fact that the pins 3| are diagonally arranged with respect to the longitudinal axes 31 of the blades 36 and are preferably disposed at an angle o. 30 with relation to the axes 31, as described in connection with the first form of the invention. As more clearly shown in Figures 9 and 13, the attaching yokes 32 are provided with inwardly projecting lugs or ribs 40, arranged to contact with the periphery the blades upon the shafts or pivots 3|, so that these blades cannot fall to, inoperative positions when the propeller is at rest, but these stops or lugs 40 do not interfere with the proper swinging movements of the blades upon their pivots 3| to vary the pitch of the same.

In Figure 11, a further modification of the invention is shown. In this figure, the yokes 32 have collars 4|, which are split, and the portions of the collars connected by bolts 42. When this construction is used the pins 3| may be formed integral with the hub 30, if desired. Y

In Figure 12, afurther modification is shown wherein yokes 43 are employed, similar to the yokes 32 but slightly elongated. 'These yokes have collars 44 formed on their ends, pivotally mounted upon shafts 45, corresponding to the shafts-3l. These shafts are rigidly attached to the hub 30. Arranged between the collar 44 of one yoke 43 and the collar 44 of the other yoke is a bevel gear 46, pivotally mounted upon a ring 41, clamped to the shaft 45. The bevel gears 46 engage gear teeth 48, as shown. The function of these bevel gears is to connect the yokes 43, thereby insuring that they swing in unison upon their pivots. However, since the propeller blades and all parts associated therewith are balanced, the blades turn in unison in opposite directions upon their longitudinal axes without the bevel gears.

In the modified forms of the invention shown in Figures 9 to 12 inclusive, a fin or blade'49 is employed in connection with each blade 36. This fin or blade 49 corresponds to the fin 25 and it may be resilient. The fin 49 has its front and rear faces fiat. Each fin 49- has an attaching extension 50, secured to the socket 34 by the bolts 34'. The fin 49 has its longitudinal axis disposed at a right angle to the longitudinal axis of the pins 3|. In order that the fin 49 may offer no substantial resistance to the air passing over the socket 34, this fin is provided with an air slot 50', near its inner end and adjacent to the socket 34. All other parts of the forms of the inventions shown in Figures 11 and 12 remain identical with that shown in connection with Figures 9 and 10 The operation of the propeller shown in Fig. ures 9 and 10, with respect to the swinging oi the blades 36 upon the diagonal pivot or pivots 3! is similar to the operation as described in connecttion with Figures 1 to 8 inclusive. The operation is diiferent to the extent that the blades 36 turn about diagonal pivot or pivots whichhave their central longitudinal axes extending through the .central longitudinal axis of the drive shaft 23.

The advantage of the construction shown in Figures 9 and 10 is that the effective areaof the blades may be increased. The blades 36, when the propeller is rotating at sea level, are at the minimum pitch and hence are inclined forwardly with respect to the radial, as shown in Figure 6,-

but when the aeroplane rises to a higher elevation, with the speed of rotation remaining the same, the blades-3G swing rearwardly toward the radial position, increasing the pitch. The operation of the propellers shown in Figures 11 and 12 is the same as those described in connection with Figures 9 and 10. The fins 49, when the propeller is rotating and the aeroplane istravelling, are

acted upon by air pressure and aid centrifugal taken as preferred examples of the same and that various changes in the shape, size, and arrangement of parts may be resorted to without departing from the spirit of my invention or the scope of the subjoined claims.

Having thus described my invention, what I claim is: 4

l. A propeller for aeroplanes and other vehicles, comprising a rotary driving element, a blade having its longitudinal axis arranged generally radially of the rotary driving element, said blade having unbalanced leading and trailing surfaces so that the resistance of the air due to the rotation of the blade will tend to move the blade about its longitudinal axis to reduce its pitch, pivot means mounting the blade upon the rotary .driving element, the pivot means having a turning axis disposed in a plane at substantially a right angle to the axis of rotation of the rotary driving element and arranged diagonally with relation to the longitudinal axis of the propeller blade, the propeller blade being free within limits to swing laterally upon the diagonal turning axis due to the action of centrifugal force for increasing the pitch of the blade, and stop ineans to positively limit the lateral swinging movement of the propeller blade upon the diagonal axis beyond such limits.

2. A propeller for aeroplanes and other vehicles,

comprislng a rotary driving element adapted to be arranged generally horizontally in use, a blade having its longitudinal axis arranged generally radially of the rotary driving element, said blade having unbalanced leading and trailing surfaces so that the resistance of the air due to the rotation of the blade will tend' to move the blade about its longitudinal axis to reduce its pitch, pivot of the propeller blade, the propeller blade being free within limits to swing laterally upon the diagonal turning axis due to the action of centrifugal force acting upon the blade for increasing the pitch of the blade, the blad swinging toward the radial position by centrifu al force, and stop means to positively limit the lateral swinging movement of the propeller blade upon the diagonal axis beyond such limits.

3. A propeller for aeroplanes and other vehicles,

comprising a-rotary driving element adapted to be arranged generally horizontally in use, a blade having its longitudinal axis arranged generally radially of the rotary driving element, said blade being so constructed that the resistance of the air due tothe rotation of the blade will tend to move the blade about its longitudinal axis to reduce its pitch; pivot means mounting the blade upon the rotary driving element, the pivot means having a turning axis which is substantially-radial with relation to the axis of grotation of the rotary driving element, said turi'rfng axis eing disposed diagonally with relation to the longitudinal axis of the propeller blade thepropeller blade being free within limits to swing laterally upon the diagonal turning iris, the propeller blade being acted upon by ce rifugal force to swing the propeller blade towai d the radial position for increasing the pitch {of the blade, stop means to limit the lateral swing ng movement of the. propeller blade beyond the limits of movement, and a fin secured to the propeller blade near the inner end of the propeller blade and near its trailing edge, the fin being acted upon by air pressure caused by the travel of the aeroplane or the like, the fin moving rearwardly with respect to the direction of travel of the aeroplane or the like and aiding the action of centrifugal force to increase the pitch of the propeller blade.

4. A propeller for aeroplanes and other vehicles, comprising a rotary driving element adapted to be generally horizontally arranged in use, yokes arranged upon opposite sides of the rotary driving element, pivot means mounting the yokes upon the rotary driving element and having a turning axis arranged radially of the rotary driving element, the yokes swinging laterally upon the turning axis in a direction longitudinally of the rotary driving element, means to limit the swinging movements of the yokes, propeller blades carried by the yokes-and extending in opposite directions, each blade having a longiareaeer tudinal axis arranged generally radially of the rotary driving element, each blade being so constructed that the resistance of the air due to the rotation of the blade will tend to move the blade about its longitudinal axis to reduce its pitch, the turning axis of the pivot means being disposed diagonally with relation to the longitudinal axis of each propeller blade, the propeller blade being acted upon by centrifugal force to swing the same toward the radial position for increasing the pitch of the blade, and a fln secured to each propeller blade near the inner end of the same and near its trailing edge, the fin being acted upon by air pressure caused by the travel of the aeroplane or the like for moving the fin rearwardly with respect to such direction of travel, the fin then aiding the action of centrifugal force to increase the pitch of the propeller.

WALTER W. EVER'I'S. 

